This invention relates to a method and an apparatus for determining human peak expiratory flow rate, to indicate to the asthmatic what course of action to pursue or what regimen of medication to follow, relative to the asthmatic's present ventilatory state.
This invention is designed for asthmatics, because these individuals have a need for determining their current lung exhalation flow rates and deviations from their own optimal or peak flow rate. This determination can help asthmatics decide or follow previously recommended remedial actions they need to take.
The onset of asthmatic symptoms may occur quickly or slowly. The faulty subjective assessment of an asthmatic's own condition by the patient can result in lack of detection of early obstruction of air passageways. If early obstruction, an early warning signal, is not detected, the patient will not exercise measures which stem worsening of the asthmatic episode. It is to the benefit of those with severe asthma, and those with mild obstruction to air passage, to be able to detect early warning signals. Those with severe asthma may have trouble relying on the more obvious warning signals which become evident too late, since an asthmatic episode may result in rapid deterioration of air exhalation flow rate. Those with mild obstruction to air passage, too, would benefit by the knowledge that they are not performing at their peak expiratory flow rate. Thus, it is important that asthmatics be able to quantify quickly and accurately the deviations from their normal peak lung flow rate in order to take appropriate remedial actions.
This invention can overcome some of the limitations which exist in the art today. An asthmatic may have somewhat narrowed airway passages which may not be detected by a physician using a stethoscope. In contrast, this invention allows detection of even subtle changes in air flow rate, giving the individual more information as to current state. With this system, a more refined approach is used in asthma management, where very moderate changes in the asthmatic's state may be countered with moderate adjustments in remedial actions.
The instrument allows the individual to take the guesswork out of self-management. The individual may check for reduced airway flow rate before bedtime, and ward off the possibility of an attack in the middle of the night. Thus, this system permits severe attacks to be warded off by allowing detection of the early warning signal, low-grade air passage obstruction. There are other "metering" devices on the market which indicate the peak lung exhalation flow of a human, yet these devices are not part of a system which quantifies the deviation from optimal peak expiratory flow in an easy and accurate manner. Use of this system yields information of lung flow rate deviation for which the user may take the appropriate remedial measures.
The system effectively acts as a biofeedback device. With it, the asthmatic learns to recognize subtle symptoms. In the long run, the asthmatic will become knowledgeable as to his or her own physiological state. Thus, the asthmatic will have learned the subtle signs that indicate mildly reduced peak expiratory flow rate, and will be able to undertake remedial actions to reduce the chance of further airflow reduction. Thus, the system helps achieve an asthmatic's long term goal of self-vigilance and accurate perception of one's state.
Today's asthmatic and in particular children may be active individuals. The devices which make up this system are very compatible with that lifestyle. In this regard, the peak flow meter itself is small, lightweight, portable, and reusable. Also, it is preferably constructed so that children may use or play with it without damaging it or resetting indicators on it. That is, the indicators used to indicate the necessity of remedial action based on the asthmatic's current expiratory flow rate should be set by a physician and should not move from the position set by the physician, despite rugged transport or handling of the device. The device is characterized by simplicity and economy of manufacture. A sleeved card which contains the compiled data is a lightweight, flat device of dimensions 4".times.8" or less. This may be contrasted with another airflow metering device available which has a vertical tower which serves as the meter, attached to a horizontal cylindrical section into which the user blows. Such an instrument would not be as convenient as the present invention for the individual to carry.
From the foregoing, it will be seen that a need has arisen for a system which integrates use of an airflow metering device into an asthmatic's active life. Need is felt for a system which detects subtle and gross changes in the asthmatic's peak expiratory flow rate, so that even a mild reduction of such flow rate is promptly dealt with in a systematic fashion. The present invention is aimed at providing such a system.
A general object of the invention is to provide an improved peak flow metering device for use by asthmatic individuals.
Another object of the invention is to provide a system to evaluate the current status of an individual with respect to peak expiratory flow rate and deviations therefrom.
These and other objects will become more apparent from the following detailed description and the appended claims.